180 Mevieu's — Professor Weinschenck — History of Graphite. 



ultimately decided, the intimate genetic relationship connecting 

 the several members of the series cannot be doubted, and this 

 foyaite-ijolite complex affords one more illustration of a number 

 of very different rock-types derived from a common source and 

 disposed in a regular order. A. H. 



IV. — Memoirs sur l'Histoire Geologique du Graphite, By 

 Professor E. Weinschenck. Compte Rendu VIII Congres 

 Geol. Internat. Paris (1901). 



GRA.PHITE, graphitite, and graphitoid are varietal names for 

 one mineral, graphite, based on subordinate characters such as 

 lustre, fracture, and compactness. The principal known occurrences 

 of graphite are reviewed. In Ceylon the graphite occurs in veins 

 traversing the (intrusive) granulites, which show contact alteration 

 in a very narrow zone immediately next to the veins. In this zone 

 the felspars are altered to kaolin and nontronite (a hydrous ferric 

 silicate), and flakes of graphite, needles of rutile, and individuals 

 of sphene appear. At Passau in Bavaria the graphite occurs in 

 lenticular masses and nests in gneissic rock of somewhat shattered 

 character; but this rock is only charged with graphite when in 

 contact with a neighbouring granite massif. The felspars are 

 altered to kaolin and nontronite, and the graphite is accompanied 

 by rutile. It is not a primary constituent of the gneiss, the flakes 

 occurring always in the fissures and joints of the rock, which have, 

 of course, originated since its crystallization. 



The graphite of the Bohmerwald occurs in an essentially similar 

 way, portions of gneiss rich in graphite having, however, a rather 

 more stratified character, related to that of the beds of limestone 

 present in the gneiss. The graphitic rocks are profoundly altered 

 as at Passau, but are not clearly associated with a large mass of 

 granite, although there are small bosses and dykes of granitic rock 

 following the direction of the graphitic bands. 



The occurrences of graphite in Cumberland and at Batongol in 

 Siberia are referred to ; the former occurs in association with an 

 eruptive ' greenstone porphyry,' the latter in connection with 

 a nepheline syenite. These two sources of graphite are no longer 

 worked. 



The alteration and impregnation products of the graphitic rocks 

 are thus similar in Passau, Bohemia, and Ceylon. In Bohemia and 

 Passau manganese peroxide is also abundant. So that the chemical 

 processes must have been the same or similar in each case. 



We might at first suppose that the hot magma in its ascent had 

 distilled and volatilized large masses of organic matter, producing 

 crystallized graphite. This would have liberated hydrogen and 

 other reducing agents ; instead we actually find that highly oxidized 

 minerals accompany the graphite. More likely the penetration of 

 carbon-bearing emanations or solutions is one of those post- volcanic 

 phenomena which may follow the intrusion of igneous rocks. The 

 metal-carbonyls — not yet met with in nature, however — easily 

 decompose to metallic oxides and graphite with loss of C O^. Professor 



